/* SPDX-License-Identifier: GPL-2.0-or-later */
/* Private definitions for the generic associative array implementation.
 *
 * See Documentation/core-api/assoc_array.rst for information.
 *
 * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#ifndef _LINUX_ASSOC_ARRAY_PRIV_H
#define _LINUX_ASSOC_ARRAY_PRIV_H

#ifdef CONFIG_ASSOCIATIVE_ARRAY

#include <linux/assoc_array.h>

#define ASSOC_ARRAY_FAN_OUT             16      /* Number of slots per node */
#define ASSOC_ARRAY_FAN_MASK            (ASSOC_ARRAY_FAN_OUT - 1)
#define ASSOC_ARRAY_LEVEL_STEP          (ilog2(ASSOC_ARRAY_FAN_OUT))
#define ASSOC_ARRAY_LEVEL_STEP_MASK     (ASSOC_ARRAY_LEVEL_STEP - 1)
#define ASSOC_ARRAY_KEY_CHUNK_MASK      (ASSOC_ARRAY_KEY_CHUNK_SIZE - 1)
#define ASSOC_ARRAY_KEY_CHUNK_SHIFT     (ilog2(BITS_PER_LONG))

/*
 * Undefined type representing a pointer with type information in the bottom
 * two bits.
 */
struct assoc_array_ptr;

/*
 * An N-way node in the tree.
 *
 * Each slot contains one of four things:
 *
 *      (1) Nothing (NULL).
 *
 *      (2) A leaf object (pointer types 0).
 *
 *      (3) A next-level node (pointer type 1, subtype 0).
 *
 *      (4) A shortcut (pointer type 1, subtype 1).
 *
 * The tree is optimised for search-by-ID, but permits reasonable iteration
 * also.
 *
 * The tree is navigated by constructing an index key consisting of an array of
 * segments, where each segment is ilog2(ASSOC_ARRAY_FAN_OUT) bits in size.
 *
 * The segments correspond to levels of the tree (the first segment is used at
 * level 0, the second at level 1, etc.).
 */
struct assoc_array_node {
        struct assoc_array_ptr  *back_pointer;
        u8                      parent_slot;
        struct assoc_array_ptr  *slots[ASSOC_ARRAY_FAN_OUT];
        unsigned long           nr_leaves_on_branch;
};

/*
 * A shortcut through the index space out to where a collection of nodes/leaves
 * with the same IDs live.
 */
struct assoc_array_shortcut {
        struct assoc_array_ptr  *back_pointer;
        int                     parent_slot;
        int                     skip_to_level;
        struct assoc_array_ptr  *next_node;
        unsigned long           index_key[];
};

/*
 * Preallocation cache.
 */
struct assoc_array_edit {
        struct rcu_head                 rcu;
        struct assoc_array              *array;
        const struct assoc_array_ops    *ops;
        const struct assoc_array_ops    *ops_for_excised_subtree;
        struct assoc_array_ptr          *leaf;
        struct assoc_array_ptr          **leaf_p;
        struct assoc_array_ptr          *dead_leaf;
        struct assoc_array_ptr          *new_meta[3];
        struct assoc_array_ptr          *excised_meta[1];
        struct assoc_array_ptr          *excised_subtree;
        struct assoc_array_ptr          **set_backpointers[ASSOC_ARRAY_FAN_OUT];
        struct assoc_array_ptr          *set_backpointers_to;
        struct assoc_array_node         *adjust_count_on;
        long                            adjust_count_by;
        struct {
                struct assoc_array_ptr  **ptr;
                struct assoc_array_ptr  *to;
        } set[2];
        struct {
                u8                      *p;
                u8                      to;
        } set_parent_slot[1];
        u8                              segment_cache[ASSOC_ARRAY_FAN_OUT + 1];
};

/*
 * Internal tree member pointers are marked in the bottom one or two bits to
 * indicate what type they are so that we don't have to look behind every
 * pointer to see what it points to.
 *
 * We provide functions to test type annotations and to create and translate
 * the annotated pointers.
 */
#define ASSOC_ARRAY_PTR_TYPE_MASK 0x1UL
#define ASSOC_ARRAY_PTR_LEAF_TYPE 0x0UL /* Points to leaf (or nowhere) */
#define ASSOC_ARRAY_PTR_META_TYPE 0x1UL /* Points to node or shortcut */
#define ASSOC_ARRAY_PTR_SUBTYPE_MASK    0x2UL
#define ASSOC_ARRAY_PTR_NODE_SUBTYPE    0x0UL
#define ASSOC_ARRAY_PTR_SHORTCUT_SUBTYPE 0x2UL

static inline bool assoc_array_ptr_is_meta(const struct assoc_array_ptr *x)
{
        return (unsigned long)x & ASSOC_ARRAY_PTR_TYPE_MASK;
}
static inline bool assoc_array_ptr_is_leaf(const struct assoc_array_ptr *x)
{
        return !assoc_array_ptr_is_meta(x);
}
static inline bool assoc_array_ptr_is_shortcut(const struct assoc_array_ptr *x)
{
        return (unsigned long)x & ASSOC_ARRAY_PTR_SUBTYPE_MASK;
}
static inline bool assoc_array_ptr_is_node(const struct assoc_array_ptr *x)
{
        return !assoc_array_ptr_is_shortcut(x);
}

static inline void *assoc_array_ptr_to_leaf(const struct assoc_array_ptr *x)
{
        return (void *)((unsigned long)x & ~ASSOC_ARRAY_PTR_TYPE_MASK);
}

static inline
unsigned long __assoc_array_ptr_to_meta(const struct assoc_array_ptr *x)
{
        return (unsigned long)x &
                ~(ASSOC_ARRAY_PTR_SUBTYPE_MASK | ASSOC_ARRAY_PTR_TYPE_MASK);
}
static inline
struct assoc_array_node *assoc_array_ptr_to_node(const struct assoc_array_ptr *x)
{
        return (struct assoc_array_node *)__assoc_array_ptr_to_meta(x);
}
static inline
struct assoc_array_shortcut *assoc_array_ptr_to_shortcut(const struct assoc_array_ptr *x)
{
        return (struct assoc_array_shortcut *)__assoc_array_ptr_to_meta(x);
}

static inline
struct assoc_array_ptr *__assoc_array_x_to_ptr(const void *p, unsigned long t)
{
        return (struct assoc_array_ptr *)((unsigned long)p | t);
}
static inline
struct assoc_array_ptr *assoc_array_leaf_to_ptr(const void *p)
{
        return __assoc_array_x_to_ptr(p, ASSOC_ARRAY_PTR_LEAF_TYPE);
}
static inline
struct assoc_array_ptr *assoc_array_node_to_ptr(const struct assoc_array_node *p)
{
        return __assoc_array_x_to_ptr(
                p, ASSOC_ARRAY_PTR_META_TYPE | ASSOC_ARRAY_PTR_NODE_SUBTYPE);
}
static inline
struct assoc_array_ptr *assoc_array_shortcut_to_ptr(const struct assoc_array_shortcut *p)
{
        return __assoc_array_x_to_ptr(
                p, ASSOC_ARRAY_PTR_META_TYPE | ASSOC_ARRAY_PTR_SHORTCUT_SUBTYPE);
}

#endif /* CONFIG_ASSOCIATIVE_ARRAY */
#endif /* _LINUX_ASSOC_ARRAY_PRIV_H */